PROJECT SUMMARY/ABSTRACT Substantial evidence reports that adjuvant hormone therapy (AHT) decrease breast cancer (BCa) recurrence and mortality, however, rates of adherence to AHT have reported to be as low as 25%, which can lead to poor survival outcomes. Side effects from AHT can negatively affect HRQOL and are one of the most commonly cited reasons for nonadherence to AHT. Patients also reported a range of barriers to AHT adherence, including: at the cognitive level, women report negative beliefs about the efficacy of AHT, low cancer recurrence fears, and a lack of behavioral cues to prevent unintentionally missing doses. At the affective level, barriers include distress about side effects and high concerns regarding the impact of its long-term use. At the interpersonal level, low family support and poor communication with providers have been associated with AHT nonadherence. However, little is known about effective AHT adherence-promoting interventions. Guided by our team?s Cognitive-Social Health Information Processing Model and health communication best practices, an evidence-based mobile text messaging intervention (Txt2Adhere) was iteratively developed with patient- centered input and clinical and behavioral evaluation. The goal of Txt2Adhere is to address 1) cognitive barriers by increasing knowledge about AHT, reinforcing AHT benefits, and providing skills for medication uptake; 2) affective barriers by normalizing feelings and providing self-management skills to manage distress and symptoms; and 3) interpersonal barriers by enhancing women?s communication skills with families and providers. In a pilot study, Txt2Adhere participants reported significantly higher adherence to AHT at 2 months, compared with a UC group. The proposed study innovatively builds on the success of our pilot study by: 1) expanding the intervention period to six months; 2) following participants for 1 year; 3) adding a wireless smart pill bottle component; and 4) including a larger sample. For the phase 1 of the proposed study, focus groups and a behavioral scientific advisory panel review will be conducted to finalize the refinement and enhancement of Txt2Adhere. During phase 2, we will evaluate the efficacy of Txt2Adhere on a diverse group of BCa patients (N=300) in comparison with a UC group, recruited from Fox Chase Cancer Center and Temple University Hospital. A total of four assessments will be conducted: baseline, 3-months, 6-months, and 12-months (6- months post-intervention) follow-ups. Outcome and process variables include assessment of AHT adherence rate (measured by AdhereTech smart pill bottles), symptom distress, theory-based variables, intervention participant satisfaction with and usage of the intervention. We hypothesize that Txt2Adhere participants will report significantly higher levels of AHT adherence rates and lower levels of symptom distress than the UC group. We will determine if the reduction in cognitive-affective barriers mediates the effects of the intervention. We will explore if being minority, younger or older moderate the effects of the intervention. The study is significant because Txt2Adhere has the potential to reduce persistent AHT nonadherence among BCa women.